Apple Magic Trackpad: Run It For "Free" and Do the Environment, and Your Wallet, a Favor.
Most of my AA powered toys and appliances demand a battery change before they are truly depleted. I can measure that there is residual charge and I can't bear to toss them in the trash so they just accumulate in my closet (not a good idea). Behold the Apple Magic Trackpad. It will use the old batteries down to their last Joule-drop and I can dispose of them with a clear conscience.
New batteries, equivalent to what Apple includes, last me about eight weeks. Before they quit I get a battery warning and two weeks later they totally die. Nicely, one can go to the System Preferences>Trackpad and at the bottom left and read "Trackpad battery level" in percent. (If the trackpad batteries are completely dead you won't see this as there is no signal that the Trackpad even exists.) Once the batteries are dead replace them with used batteries and note the starting level. I have had previously used batteries read as high as 95% potency. These used batteries won't last as long as new ones but it is not a chore to keep them handy and replace them a bit more often.
A few sensible words of caution. Use only two of the same kind of batteries (don't mix lithium and alkaline). Check them to make sure they are not swollen, misshapen or leaking (leaking chemicals can be poisonous or corrosive and will mess up your battery compartment). If possible use two old batteries from the same source, starting off at the same charge is better. Don't put them in backwards. A good way to remember is the flat side is negative and goes up against the battery door which has slot in it that looks remarkably like a "negative" sign (another intuitive apple UI). I keep one of the dimes I saved to open the battery compartment. Oh, and don't over tighten it, just a slight snug will do.
Finally, if you ruin your nice Trackpad, it is not my fault. I haven't saved so many dimes that I can send you and your attorney on a South Sea vacation.